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Constellations and Asterisms

Constellations are patterns of stars visible to the unaided eye, or regions of space seen from Earth that are bounded by borders designated by the International Astronomical Union. Asterisms are also naked-eye star patterns, but they do not form constellations on their own. An example is the Big Dipper, which is part of Ursa Major. Americans know northern hemisphere constellations by the names given them by ancient Babylonians and Greeks. Seafaring explorers named those in the southern hemisphere. Every culture created its own constellations, although most of those in use today came from western sources.